Join BayouShooter For Free
CS

Page 1 of 4 12 ... LastLast
Results 1 to 10 of 37
  1. #1
    ESSAYONS

    User Info Menu

    AR10 Last Round Hold Open Issue - Updated 02/11/2019

    So I built my first AR-10. It's mostly Aero Precision for compatibility reasons, upper (including parts kit), lower (including parts kit), BCG, and carbine buffer kit. It has a Ballistic Advantage 14.5" barrel with a pinned muzzle device. Because it was pinned before I realized I hadn't thrown the barrel nut on there, I am using a Yankee Hill Machine Specter 2 piece gas block (YHM-9378). I put a few rounds of 145gr and 150gr to test it out using both PMAGs and HexMags. In any combination of rounds and magazine, the rifle cycles fine but the bolt does not lock back on the last round. I've manually pulled the bolt back and it does reach the bolt release but there seems to be a good bit of added pressure needed to go from the point where the next round will pick up to where the bolt will catch.

    At this point I'm trying to avoid an adjustable gas block. If that's the only true fix, so be it. But I'm civil service and don't make bank so if I can spend that $130 on bills instead of a 2 piece adjustable, I won't complain. I've also read a number of suggestions for a fix. Switch out the 308 buffer spring for a 223 buffer spring. The 223 has tighter coils and I would suspect the buffer tube/bcg wouldn't be able to travel as far back so that would seem like it would make the problem worse. Another suggestion was to take fine sandpaper to the rails on the bcg so it has a bit more room/less friction to travel. But the bcg doesn't seem to have an issue. The other suggestion was to cut a loop off the buffer spring to allow more travel, and slightly less resistance, for the bcg.

    This rifle will host a can once it's finally released (8 months and counting so far).

    *I realize AR-10 is Armalite and Areo uses the DPMS LR-308 pattern. I'm using AR-10 in the generic.
    Last edited by thperez1972; February 11th, 2019 at 05:07 PM.

  2. #2
    Marksman

    User Info Menu

    Wait until you get your can. I have found (and many others) that the AR-10 (generic term) is harder to suppress than a 5.56 gun. Meaning it is tougher to get them to run consistent with/without can and with different rounds. Your can will likely change the dynamic significantly on that rifle.

  3. #3
    Marksman

    Premium Member

    User Info Menu

    Two things I can think of... Are you sure you have the correct DPMS pattern buffer it should be 3/4" shorter than a standard AR15 buffer.

    Second is that the gas block needs adjustment. Your ejection should be about 2-3 o'clock. 1 o'clock is way over gassed. Also 4-6 o'clock is undergassed. My Ar10's needed some finagling if the barrel was not dimpled....

    If changing position of the gas block does not help change the gas block...
    Motorcycles and guns, how fun....

  4. #4
    All or nothing

    User Info Menu

    I’m assuming you’ve got the correct spring and buffer from what you stated about the build, but I’ve seen people use a carbine buffer in a rifle stock and vice versa. Not saying you don’t know what you’re doing but you did state first 08 build. Gas (or lack of) is always a strong possibility when dealing with BCG travel issues. But if the rifle is cycling and peeling the next round from the mag without fail, chances are the BCG is traveling far back enough to lock on the empty mag. It may clear up after break in. Also try shooting the rifle in a sled or hug a post and fire the gun with the post between your shoulder and the butt stock with one round in the mag. I’ve got 2 pistols that a few other people can’t seem to shoot without a failure to cycle the next round and it never happens for me. Once they get a firm grip and bow up to the recoil it functions fine.
    Contrary to popular belief, a head shot is not necessarily a guaranteed kill shot....but it sure does take the fight out of 'em.

    and if one in every 100,000,000 M&M's contained enough cyanide to kill a person, the Mars candy company would be forced by public outcry to correct it———
    Bangswitch

  5. #5
    ESSAYONS

    User Info Menu

    It is the shorter buffer. And it's a carbine length spring in a carbine length buffer tube. And hopefully one of my cans will come in soon (one ais at 6 months, the other at 8 months). I'm going to pull off the gas block to make sure it's lined up correctly.

  6. #6
    All or nothing

    User Info Menu

    Quote Originally Posted by thperez1972 View Post
    It is the shorter buffer. And it's a carbine length spring in a carbine length buffer tube. And hopefully one of my cans will come in soon (one ais at 6 months, the other at 8 months). I'm going to pull off the gas block to make sure it's lined up correctly.
    Sounds like a plan. Hopefully you’ll get it sorted out before you get your suppressor in case you’re planning on shooting subs. And if you do, try the Sellier&Bellot. They work great in mine.
    Contrary to popular belief, a head shot is not necessarily a guaranteed kill shot....but it sure does take the fight out of 'em.

    and if one in every 100,000,000 M&M's contained enough cyanide to kill a person, the Mars candy company would be forced by public outcry to correct it———
    Bangswitch

  7. #7
    Marksman

    Premium Member

    User Info Menu

    Since you have DPMS pattern lowers your welcome to meet up and swap with my known good DPMS pattern lowers and uppers. Always love an excuse to break out the 10.5" AR10 pistol lol.
    Motorcycles and guns, how fun....

  8. #8
    Marksman

    Gold Member

    User Info Menu

    If it's undergassed, which it sounds like it may be, an adjustable gas block won't help. I've had some bad luck with the YHM 2-piece gas blocks, make sure you've got it perfectly aligned over the gas port and the screws properly torqued with thread locker. The suppressor will add a little more backpressure and likely fix the issue, but I'd still try to get it running right unsuppressed as well.

  9. #9
    Marksman

    User Info Menu

    I have a DPMS AR-10 (18") I bought new, it had "feeding problems" thought it was under-gassed, turns out it was over-gassed. I drilled out the gas port in the barrel. Seems as thought port size changes with location due to barrel length. I have two weapons, one with an 18" and one with a 24" barrel. If I remember 18" had a .063" hole and 24" maybe like a .078" hole. I drilled the .063" out to .078" and installed a JP industries adjustable regulator. Shut it off, put one round in the mag fired it, opened the the regulator until it locked back. Never had problems with since. Here is the funny part, since I put the regulator on the gun It literally tripled the accuracy of the gun. I have made multiple trips to the range over the last few years with it thinking the groups the gun shot was a fluke. Summer, winter, gun clean or dirty it will shoot .750" (.375 MOA) groups all day at 200 yards. This is no B.S. I have never seen any thing like it?
    Last edited by Expert684; January 2nd, 2019 at 01:02 PM.
    One team, one mission, only one result! Seals 1 Bin Laden 0

  10. #10
    ESSAYONS

    User Info Menu

    Quote Originally Posted by sportsbud View Post
    Since you have DPMS pattern lowers your welcome to meet up and swap with my known good DPMS pattern lowers and uppers. Always love an excuse to break out the 10.5" AR10 pistol lol.
    Sounds good. The next time I'm in NO, we can go out to the lower 9th ward and shoot at the burned out cars.

    Quote Originally Posted by SpeedRacer View Post
    If it's undergassed, which it sounds like it may be, an adjustable gas block won't help. I've had some bad luck with the YHM 2-piece gas blocks, make sure you've got it perfectly aligned over the gas port and the screws properly torqued with thread locker. The suppressor will add a little more backpressure and likely fix the issue, but I'd still try to get it running right unsuppressed as well.
    That's the ultimate goal.

    Quote Originally Posted by Expert684 View Post
    I have a DPMS AR-10 (18") I bought new, it had "feeding problems" thought it was under-gassed, turns out it was over-gassed. I drilled out the gas port in the barrel. Seems as thought port size changes with location due to barrel length. I have two weapons, one with an 18" and one with a 24" barrel. If I remember 18" had a .063" hole and 24" maybe like a .078" hole. I drilled the .063" out to .078" and installed a JP industries adjustable regulator. Shut it off, put one round in the mag fired it, opened the the regulator until it locked back. Never had problems with since. Here is the funny part, since I put the regulator on the gun It literally tripled the accuracy of the gun. I have made multiple trips to the range over the last few years with it thinking the groups the gun shot was a fluke. Summer, winter, gun clean or dirty it will shoot .750" (.375 MOA) groups all day at 200 yards. This is no B.S. I have never seen any thing like it?
    So the idea it to purposely over-gas the rifle so it can be regulated by the adjustable gas block?

    What gas block are you using? They make one of the only 2 adjustable 2 piece gas blocks I could find.
    https://www.jprifles.com/buy.php?item=JPGS-9D

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •